A portable hand-held communication device, such as a cellular telephone, typically has less than fifteen keys available for data entry of information for short messaging and address book features. FIG. 1 shows a prior art reduced keypad 100 for an electronic device. The prior art reduced keypad shown is a standard telephone keypad having ten number keys 110-119, a star (*) key 121, and a pound (#) key 122. For English and many other alphabet languages, the numeric keypad of the telephone is overlaid with an alphabet keypad where three or more letters of the alphabet are associated with each number key. For example, the five (5) key 115 is associated with the letters j-k-l. In some reduced keypad electronic devices, upon entering an alphabet entry mode, a user employs multiple key presses to enter letters to make words and names for use by features such short messaging and address book.
For example, once in alphabet entry mode, a user can employ one keypress to select the first letter associated with a depressed key, two keypresses of the same key to select the second letter associated with the key, three keypresses of the same key to select the third letter associated with the key, and so on. Letters are separated using a confirm key, such as the pound (#) key 122.
Chinese and other character-based languages such as Japanese kanji, however, do not have a manageable number of alphabet letters that can be overlaid onto a numeric keypad. For example, Chinese does not use an alphabet and instead has about 5000 to 7000 commonly-used characters. Advantageously, many phonetic systems have been developed to standardize the pronunciation of, for example, Mandarin Chinese. Several of these phonetic systems use the roman alphabet as phonetic symbols, such as the Wade-Giles and the pinyin systems for Mandarin Chinese, and other phonetic systems use a unique phonetic symbol set, such as the zhuyin system for Mandarin Chinese which has a 37-symbol phonetic alphabet. Cantonese Chinese also has a phonetic system using the roman alphabet.
Although there are over 5000 commonly-used Chinese characters, there are only approximately 400 basic phonetic syllables in Mandarin Chinese speech. Thus, the same Mandarin Chinese phonetic syllable is used by many different Chinese characters. An extreme example is the Mandarin Chinese pinyin word "yi"; this phonetic syllable represents over 100 different Chinese characters, each with a different meaning.
Additionally, Mandarin Chinese uses four standard tones to differentiate meanings. Thus, the same phonetic syllable, when pronounced using a different tone, has a different meaning. Using the phonetic word "yi" as an example, at least 20 characters use the first tone, at least 31 characters use the second tone, at least 16 characters use the third tone, and at least 63 characters use the fourth tone.
Although there exist various methods of entering Chinese characters into a computer system using a full-sized keyboard having keys corresponding to all of the phonetic symbols of one of the various phonetic systems and the four tones, there is a need for a reduced keypad entry method for characters for use in a portable hand-held device such as a cellular telephone.